What is a "train order"?

Answer: B — directive issued to train crews

A "train order" is a directive issued to train crews that provides instructions regarding operations on the railway. These orders can include information such as changes in the schedule, special instructions for approaching railroad junctions, or specific operating procedures that need to be followed by the crew. They are crucial for ensuring the safe and efficient operation of trains, especially in situations where traditional signals may not provide sufficient guidance. This definition highlights its primary role in coordinating train movements and maintaining safety on the railway network. Other options, while they pertain to different aspects of train operations, do not capture the essence of a "train order" as it relates to direct instructions given to the crew.